Prostate cancer currently affects a significant number of men, particularly those in the age bracket of 50 to 80. In 1997 alone, 230,000 men will be diagnosed with prostate cancer. In the past, prostate cancer has often been diagnosed only when it was in an advanced and virtually incurable state. With the introduction of certain diagnostic measures, however, including the PSA blood test, as well as heightened public awareness, prostate cancer is now often being diagnosed at a relatively early and curable stage.
There are three fundamental treatments for prostate cancer, including radical prostatectomy (surgery), external beam radiation, and radioactive seed implantation. Radical prostatectomy has historically been very effective, but also has a relatively high rate of impotence, incontinence and surgical morbidity associated with it. External beam radiation has been reasonably effective for treatment of early stages of prostate cancer and has fewer side affects than radical prostatectomy. Beyond the early stages of the disease, however, external beam radiation decreases in effectiveness relative to the surgical procedure. The third technique, radioactive seed implantation, involves the placement of radioactive seed-like elements in the prostate gland. The radioactive seeds deliver high dosages of radiation to the prostate, but relatively low dosages to the surrounding tissue, such that the radiation is quite targeted to the prostate, resulting in the destruction of cancer cells in the prostate before they can spread to other parts of the body.
The original seed implantation procedure was an "open" implant technique. In this technique, the radioactive seeds were placed directly into the prostate gland through a surgical incision. However, this type of implant has proven to be relatively unsatisfactory, since the seeds are difficult to position properly.
A recent development involving radioactive seed implantation is referred to as transperineal seed implantation. This technique, which is described in more detail below, has had excellent results, generally equal to surgery (radical prostatectomy). Also known as brachytherapy, this technique is advantageous in that it can be performed on an outpatient basis, permitting the patient to resume normal activities in just a few days. The technique has proven to have relatively low incontinence and impotency rates and therefore has become increasingly attractive.
The goal of the transperineal technique is to significantly increase the accuracy of the placement of the radioactive seeds into predetermined locations within the prostate gland. This increase in accuracy is believed to account for the significant success rate of the technique and the other advantages discussed above. The transperineal technique uses a plurality of needles (typically 25-30 per treatement) to position the seeds within the prostate. The needles are used with a specialized stepper apparatus, an ultrasound probe and a template, for initially positioning, guiding and then moving the needles to proper placement within the prostate.
The needles currently used with the transperineal technique do have some disadvantages. The insertion of the needles can (and typically will) result in movement of the prostate. Because the seeds are designed to be placed in precise locations within the prostate, this movement of the prostate can result in seeds being slightly off the desired target area. Stabilizing needles have been used to attempt to minimize this disavantage, but they have not been completely successful and are expensive.
Further, the existing needles are loaded with the radioactive seeds prior to their insertion, along with spacer elements which separate adjacent seeds. Since the needles are metal, confirmation that the needle is correctly loaded is either not done or accomplished by radiographic examination, which can be time-consuming, somewhat difficult and is fairly expensive. It would be desirable to be able to verify the correct loading of the seeds more readily and quickly.
Still further, it is known that, in actual practice, five or more insertions per needle are typically necessary to position each needle correctly. This may result in significant trauma to the prostate, considering, as indicated above, that 25-30 needles are needed per treatment. Swelling of the prostate typically results, which also affects the accuracy of subsequently inserted needles. The accurate and proper placement of the needles is very important to the successful use of the seed implantation.
Significant experience in use of the technique is also important to its success. However, if one or more of the above-described disadvantages can be significantly reduced, then experience becomes somewhat less of a factor. This is important in the present situation, where the need for the technique is quite high and large numbers of physicians are undertaking initial training in the technique. The easier and more reliable the technique, the more quickly a physician can attain a high success rate.